Heretofore, different welding equipment has been required to perform the different types of welding, such as rod, MIG or TIG welding, each type of equipment being specifically designed for a single welding purpose. This requires that to carry out a range of welding work, several different electric welders are necessary.
Further, to enable an ordinary arc welder to be used as a MIG or TIG, it is necessary to provide controls which include control of striking the arc, wire feeding, purging and operation timing. For more reliable welding, a MIG (or TIG) has control circuits which cause the transformer core to saturate. This saturation of the core generates third harmonics which produces a substantially square wave output which facilitates arc striking and maintenance.
When adding control equipment to an ordinary arc welder in order that it can operate as a MIG, it is desirable to produce a substantially square wave output. However, the core structure of an ordinary welder has inappropriate iron to enable production of the desired square wave output.
It is desirable to provide apparatus whereby arc welding equipment may be adapted to be used either as a spot welder, or a MIG or a TIG welder or stud welder.
It is also desirable to provide such apparatus which includes apparatus operable to automatically adjust a wire feed control on a wire-fed welder whereby the wire feed is proportional to the welding arc and, consequently, the use of the filler metal.
It is also desirable to provide apparatus whereby, when set up for use as a MIG or TIG, the rectified output from the welder transformer approaches a square wave.
It is also desirable to provide improved gas purging control for a gas-shielded welder to prevent waste of inert gas during welding and to avoid delays otherwise experienced due to gas purging requirements.
It is also desirable to provide control apparatus for an arc welder to facilitate use as a spot welder with circuitry for welding control to produce even spot welds for welding or tacking purposes.